Astro-E II

Astro E was supposed to be the fifth in the series of Japanese X-ray satellites. Its overall soft X-ray effective area and mirror design were similar to those of ASCA, except that its mirrors had a factor of two improvement in spatial resolution. In addition to soft X-ray CCD detectors, Astro E had a hard X-ray detector that was sensitive to energies as high as 700keV. Most importantly, however, Astro E was to utilize the first space-based X-ray micro-calorimeters. Rather than achieve high spectral resolution via dispersion gratings, X-ray photons would deposit heat into calorimeter elements with eV energy resolution, thus achieving $E/\Delta E \approx 1000$ or more at 6keV. The calorimeters required cryogenic cooling, limiting their useful lifetime to approximately two years. Thereafter, however, the remaining Astro E detectors would have had comparable energy resolution to that of the ASCA CCDs, and broader energy coverage (0.3-700keV) than either RXTE or BeppoSAX. The first Astro E satellite was launched in early 2000. Unfortunately, attitude control of the launch vehicle was lost, and Astro E was placed in a shallow, elliptic orbit, from which it fell to Earth a short while later. Following much the original design plan, however, the Astro E2 mission is currently being built. It will have all of the originally intended capabilities of Astro E, and a successful launch is expected in 2005. NASA is a major collaborator in this endeavor.